The term 'E-Mail Predecessor' refers to the communication methods that preceded the invention of e-mail. The three solutions for this term are LETTER (6 letters), telex (5 letters), and TELEGRAM (8 letters). A LETTER is a written message sent through the postal service. Telex was an early form of electronic communication that used teleprinters to send messages over telephone lines. TELEGRAM was a service that allowed people to send short messages via telegraph. All three of these methods were used before the invention of e-mail, making them predecessors of the modern form of communication.